The Research Of Heat Treatment Process Of Bmicroalloyed Steel Plate

To develop marine engineering equipment and key materials of localization is animportant transformation of the strategic level. Quenched and tempered steel platetype requires a good strength and toughness at high strength, high toughness, theproduction is great difficult. Firstly, study of a comprehensive the performance ofB-containing alloy elements of the plate the thickness of which60mm marineengineering is carried out. According to the characteristics of the plate productionprocess, and quenching process in different parts of steel of the laboratory issimulated, heat treatment trials is carried out,a detailed study of the relationshipbetween the heat treatment process, the microstructure and mechanical properties,providing a theoretical basis and guidance for industrial productionIn order to study the performance of the hardenability of thick steel, did endquench test experimental in this paper is did about several common B microalloyedsteel,results prove that hardenability of B for thick steel and the important influenceof the alloying elements such as Al on hardenability impact of B. The study found thathigher levels of micro-Ti and Al can effectively inhibit the precipitation of BN, toensure effective solid solution of B and to strengthen the micro-alloying effect of B;while the inhibition of V for BN is weak. The quenching process affected significantlyby the grain boundary segregation of B in steel. In this paper, after that, CCT curveswere measured about a steel of relatively good hardenability, hardness andmicrostructure in continuous cooling down arrived at the CCT curve of theexperiments steel.Simulation test in the laboratory is carried out about plate quenching,respectively, after the test steel austenitized, water-cooled, oil cooling, air cooling andfurnace cooling,cooling in four different ways is carried out, arrvied varyingproportions of lath martensite/shellfish organization. With the decrease of thecooling rate, bainite content gradually increased, the tensile strength increases slightly,but the range of variation is small, the yield strength is reduced to a lesser extent, under the oil cold state obtain the best overall performance. And the oil cooler is thebest choice.Then after the oil cooler on the experiment carried out at different temperaturesaustenitizing steel tempering, thus optimum heat treatment process.For thick steelplate under the component system, the optimum quenching temperature is900℃,optimum tempering temperature is640℃. In the quenching process of60mm plate ofIndustrial production,typically lath martensite is obtained in the surface, andmartensite/bainite (M/B) of the mixed structure is obtain in the core section,Comprehensive analysis results showed that the differences in the organization of thesteel sheet between surface and the center is the cause to obtain an excellentlow-temperature toughness in the central portion of the steel sheet. There is littlechange in strength and ductility from surface to the center of each part, while theductility of the central portion of the steel sheet was superior than the surface, in lowtemperature at a test temperature of-60℃, the impact value of the toughness of thesteel sheet to achieve core section130J, and the surface only30J.